The new nylon and Teflon pancreatic stents compared to polyethylene for patency and stent induced changes in dog pancreas

Polyethylene stents placed in dog pancreatic ducts have been reported to cause significant morphologic changes in the pancreas. Nylon and Teflon material appear to cause less tissue reactive changes than polyethylene. AIM: To determine the effect of polyethylene, nylon and Teflon stents on pancreatic morphology and stent patency. METHOD: Following laparotomy and duodenotomy, stents were placed in 8 mixed breed dogs after a baseline pancreatogram. In group I (6 dogs), 2 nylon, 2 Teflon, and 2 polyethylene stents (5F, 3cm) were placed in the main PD and left in for 8 weeks. In group n (2 dogs), 1 nylon and 1 Teflon stent was placed in the main PD for 4 weeks. After the initial 4 weeks, the stents were removed and pancreatogram and stent patency test were performed. Stents were replaced in the 2 dogs, and at 8 weeks, the stents were removed from all dogs and pancreatogram, stent patency tests and histology were performed. Histologic changes were based on the degree of ductal change, fibrosis, and atrophy and grades as mild, moderate, and severe. RESULTS: In group I, the stents of all 3 materials were completely occluded and severe histological changes were found in all 6 dogs. In group II, at 4 and 8 weeks, the nylon stent was partially patent with a normal pancreatogram; the polyethylene stent was completely occluded with side branch changes on the pancreatogram. At 8 weeks, severe histologic changes were noted in the dog with the polyethylene stent but only mild changes with the nylon stent. CONCLUSION: When stents were left in for 8 weeks, all stent materials resulted in complete occlusion and severe histologic changes in the pancreas. However with the nylon stent changed at 4 weeks, patency was preserved and only mild histologic changes were evident. This potential benefit of the new nylon stent needs to be established in clinical trials.